Unburned refractory brick



Patented Sept. 20, 1927.

UNITED STATES 1,643,181 PATENT OFFICE.

GEORGE K. SGHLOTTEBEB, OI CHESTER, AND ROBERT H. YOUNG-HAN, OI PITTSBURGH, IENNSYLVANIA, ASSIGNORS TO HARRISON-WALKER REFBACTOBIES COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORFOBATION OI PENNSYLVANIA.

.UNBUBNED REFRACTORY BRICK.

Io Drawing.

This invention relates to refractory bricks and shapes, and more particularly to those composed of dead-burned magnesite bound together with sodium silicate, molded to shape and dried, but not burned after mold- The general ob'ect of the invention is to make a basic rick or shape of deadburned refractory material, such as maginesite, stron enough to be handled, store shipped, an built into furnaces or the like without burning and without deterioration from atmos heric exposure. These objects are secured y a special bonding, setting and drying treatment. Although brick are primarily intended, and are spoken of throughout this specification, it will. be understood that analagous shapes are included.

Refractory compositions in brick form comprising dead-burned magnesite and simil r refractories are well known. Also combiiiations of such refractory materials with binders of various kinds, including sodium silicate, and for various urposes, are known. But heretofore it has not been practicable to make bricks from previously dead-burned magnesite with sodium silicate as a binder, without burning after molding, although sodium silicate has long been known and used as a binder in connection with refractories and has even been tried experimentally with dead-burned magnesite for making brick, but without ractical success, unless the brick was burn after mold- 36 in The diflicult has been that sodium silicate with deadurned magnesite seemed to lack suflicient'strength as a bond for brick when used in a permissible proportion. Dead-burned magnesite is quite porous and absorptive, and tends to soak up a liquid binder readily. If eno h sodium silicate is used to make a hard s arp brick without burning the refractory property of the brick is too low. If an amount ess than 10% of sodium silicate is used, the binder seems to be absorbed by the ma esite, and the result is a crumbly brick o insufiicient strength for handling and use, unless it is burned.

Sodium silicate has the pro rty of sticking and setting hard and can b: mixed with magnesite either in solution or dry, water to be added after mixing. It has been used successfully for makin unburned brick of chrome, as for examp e that described in Application filed Kay 15,

'of deadburned magne'site, by bindin with not over 10% of sodium silicate, an then putting ,the molded brick or shape through a special setting and dry' fifiocess, initially in a humid atmosphere. 5 special setting and drying makes possible the production of an unburned magnesite brick with not over 10% of sodium silicate binder.

The preferred application of this invention is the mixture of from 90 to 95% of dead-burned powdered ma 10 to 5% of dry powder sodium silicate, then the addition of suflicient water to seesite with from cure plasticity, molding or pressing into the.

required bric or shapes, and then drying.

Sodium silicate in solution may be used instead but there are very decided advantages to the dry mixture and addition of water. The result is a strictly basic brick. While the process described may be valuable for other porous refractory products where a binder of sodium silicate is used, the most valuable application of the invention alppears to be in the making of a commercia y acceptable unburned brick from dead-burned magnesite and sodium silicate, such a rod-- uct having been previously very muc desired by the trade, but not available by previously used dplil'ocesses of makin After mol 5 the moist bricks are put through a speci setting and dryin process. This consists in placing the moist ricks or shapes as they come from the press on rack cars which are then moved to a tunnel dryer in which there is complete control of humidity within from saturation down.

freferably t e bricks are set and dried in stages, the first, which may be called an initial sett' stage, is continued for about ten hours, t e humidity being maintained from u ward, and the temperature at about 130 ahrenheit. The second stage, which may be called a set and drying period, lasts for about thirty ours, the huatmosphere 0 midity being reduced to about 60% and the near zero as possible. For example, heating to 180 for about seventy-two hours, or 120 for about one hundred forty-four hours, appear to be substantially equivalent to the time and temperature first mentioned for this third stage.

After the bricks have gone through this gradual setting and drying process at low temperatures, and initially set in an atmoshere of high humidity and comparatively lbw temperature, they are found to be hard, dry, of strong structure, permanently bound, and they may be stored for long periods without deterioration from atmospheric exposure. They are strong enough to stand handling, shipment, and use, and consequentl without any further treatment may be bui t into furnace structures with satisfactory results.

It is believed that the temperatures, times and humidity ercentages above given are not critical, and that these elements may be varied within a reasonable range. The ranges and stages given are those that have been found in actual production to be practicable and so far as observation goes, appear to be those best suited for attaining the desired end.

The material elements of the process seem to be that the moist bricks from the press shall go through a sta e of initial setting in an atmosphere of big humidity, followed by a slow. drying treatment, at comparatively low temperature. The humidity is reduced progresslvely and the drying terminates in a period of a plication of mild heat in an minimum or zero humidity. Just what the individual effects of these steps are is not fully apparent. Probably the setting of the sodium silicate takes place in the first two stages, in the presence of considerable moisture, and this revents its migrating to the surface and its orming into crystals. The results seem to be to permit the sodium silicate by this setting slowly and initially in a moist air, to bind uniformly throughout the brick without crystalliamg unequally as it apparently has a tendency to do when the moist brick is heated initially in a dry atmosphere. At any rate, this process of drying results in a hard,

' strong, permanent structure when the brick is finally dried, with a permissible amount of binder, whereas the methods heretofore used have not produced a brick that could be stored, shipped, and built into furnaces. Consequently it has heretofore been considered and in fact has been impracticable to produce commercially acceptable unburned brick of dead-burned magnesite bonded with sodium silicate.

The many advantages of an unburned brick of dead-burned magnesite with low percentage of binder strong enough to handle and shi without having to undergo the expense of urning will be readily apparent to those familiar with the art of manufacture and use of such bricks.

We claim:

1. In the making of unburned refractory brick comprising a binder of sodium silicate, the process of initially storing the raw brick for a material period in an atmosphere of high humidity. i

2. In the making of unburned refractory brick comprising a'binder of not over 10% of sodium silicate, the process of initially storing the raw brick for a material period in an atmosphere of hi h humidity.

3. In the making 0 unburned refractory brick comprising a binder of sodium silicate, the process of initially storing the raw brick in an atmosphere of high humidity, then drying in an atmosphere of comparatively low humidity.

4. In the making of unburned refractory brick comprising a binder of sodium silicate, the process of initially storing the raw brick in an atmosphere of high humidity and comparatively ow temperature, thereafter drying the brick in an atmosphere of comparatively low humidity and increased temperature.

5. In the making of unburned refractory brick comprising a binder of sodium silicate, the process of treatment comprising first slightly heating the raw brick in an atmosphere of high humidity for a material period, and thereafter progressively reducing the humidity until the brick is dry.

6. In the makin of unburned refractory brick comprising a inder of sodium silicate, the process of treatment comprising first slightly heating the raw brick in an atmosphere of high humidity for a material period, and thereafter progressively decreasmg the humidity and increasing the temperature until the brick is dry.

7. In the making of unburned refractory brick com rising dead-burned magnesite with a bin er of sodium silicate, the process of initially storing the raw brick for a setting period in an atmosphere of high hum1 ity.

8. In the making of unburned refractory brick com rising dead-burned magnesite with a bin er of not over 10% of sodium silicate, the process of initially storing the raw brick for a setting period in an atmosphere of high humidity.

9. In the making of unburned refractory brick comprising dead-burned magnesite with a .binder of sodium silicate, the process of initially storing the raw brick for a settin period in an atmosphere of high humi ity, then drying in an atmosphere of comparatively low humidity.

10. In the making of unburned refractory brick comprising dead-burned magnesite with a binder of .sodium silicate, the process of initially storing the raw brick for a setting period in an atmosphere of high humidity and comparatively low temperature,

thereafter drying the brick in an atmosphere of comparatively low humidity and increased temperature.

11. In the making of unburned refractory brick com rising dead-burned magnesite with a bin er of sodium silicate, the process of treatment comprising first storing the raw brick in a. warm atmosphere of high humidity for a material period, and thereafter progressively. decreasing the humidity until the brick is dry.

12. In the making of unburned refractory brick comprising dead-burned magnesite with a binder of sodium silicate, the rocess of treatment comprising first storing t e raw brick in a warm atmosphere of igh humidity for a material period, and thereafter comprising the steps of initially storing the I raw brick in an atmosphere of not less than humidity for a period'of not less than ten hours, and thereafter drying the brick in an atmosphere of reduced humidity and increased temperature.

14. The process 01 making unburned refractory brick consisting of dead-burned magnesite with a binder of sodium silicate, comprising the steps of initially storing the raw brick in an atmosphere of not less than 75% humidity for a period ofnot less than ten hours, then storing the brick for a secondary setting period in an atmos here of not less than 60% humidity for a onger time, then drying.

15. A finished unburned basic refractory brick comprising dead-burned magnesite and a binder of sodium silicate.

16. A finished unburned refractory brick comprising not less than of dead-burned magnesite, and not more than 10% of sodium silicate.

In testimony whereof, we hereunto sign our names.

GEORGE K. SCHLOTTERER. ROBERT H. YOUN GMAN. 

